Devices for applying forces

ABSTRACT

A shear comprises two co-operating force-applying members such as blade holders with a shear blade, one of the members is coupled to a short stroke reciprocatable drive member such as a rotary eccentric and a crosshead, and one of the members is connected to a variable spacing device which is in the form of at least one piston and cylinder, the cylinder is sealed off during movement of the drive member in one direction and the cylinder is permitted to move relative to its piston in the reverse direction of movement of the driving member so that a workpiece can be cut in a series of shearing operations.

[451 May 1,1973

[54] DEVICES FOR APPLYING FORCES [75] Inventor: Bela Istvan Bathory,Yorkshire, En-

- gland [73] Assignee: Davy and United Engineering Company Limited,Sheffield, England [22] Filed: Feb. 2, 1971 [21] Appl.No.: 111,996

[30] Foreign Application Priority Data [56] References Cited UNITEDSTATES PATENTS 167,202 8/1875 Stunnard ..83/527 1,796,356 3/1931 Beatty3,279,292 10/1966 Beard ..83/639 X 3,077,134 2/1963 Ronick ..83/639 X3,473,427 10/ l 969 Leibinger ..83/527 3,453,914 7/1969 Lemper et a1.....83/554 X 3,081,659 3/1963 Theobald ..83/554 FORElGN PATENTS ORAPPLICATIONS 2,721 2/1915 Great Britain ..l00/271 PrimaryExaminer-Andrew R. Juhasz Assistant ExaminerJames F. CoanAtt0rney--Henry C. Westin [57] ABSTRACT A shear comprises twoco-operating force-applying members such as blade holders with a shearblade, one of the members is coupled to a short stroke reciprocatabledrive member such as a rotary eccentric and a crosshead, and one of themembers is connected to a variable spacing device which is in the formof at least one piston and cylinder, the cylinder is sealed off duringmovement of the drive member in one direction and the cylinder ispermitted to move relative to its piston in the reverse direction ofmovement of the driving member so that a workpiece can be cut in aseries of shearing operations.

9 Claims, 3 Drawing Figures Patented May 1, 1973 I5 Sheets-Sheet 1Inventor QELA mm annonv x M! Y 0. 'I'TI Attorney Patented May 1, 19733,730,036 I 3 Sheets-Sheet 2 Inventor QELA} ISTVAN QATHORY- y HENRY O.WEQT'N Allarm'y Patented May 1, 1973 3 Sheets-Sheet 5 Inventor BELAISTVAN QATHQRY y HENRY a. warm DEVICES FOR APPLYING FORCES Thisinvention relates to devices for applying forces to workpieces,particularly of metal. The invention is primarily concerned with ashear, which is operated by relatively short stroke reciprocating meansand which applies a high force over a relatively long distance. Thus theinvention is applicable to a shear for progressively cutting a thickmetal workpiece in a series of cuts.

In such a shear there is a driven member which is reciprocated towardsand away from the workpiece with a throw considerably less than themaximum workpiece thickness to be sheared and a variable spacing deviceconnecting the driving member with one of the blade holders. Thisspacing device transmits the movement of the driving member to the bladeholder during the motion of the latter in this cutting direction; on thereturn movement of the driving member, the spacing device is operated toincrease the spacing between the driving member and blade holder, sothat on the next cycleof the driving member, a further cut is effected.The cycles of the drivingv member continue until the entire thickness ofthe workpiece is sheared.

The problem of such a shear is centered on the difficulty of adjustingthe spacing device appropriately in the small time period availableduring the return motion of the driving member. To be effective theshear must perform the entire shearing action in a limited space oftime; with the limited movement available from, say, an eccentric, anumber of reciprocations must be effected in this time, with the resultthat the adjustment of the spacing device must be performed quickly. Ifthe spacing device is a screw for example, it must be heavy and robustto stand up to the duties it is required to perform and this in turnentails powerful motors to accelerate and drive the device.

According to the present invention a shear comprises two cooperatingforce applying members, a reciprocatable drive member coupled to one ofthe force applying members and a variable spacing device connected toone of the force applying members, the variable spacing device being inthe form of at least one piston and cylinder the cylinder of which issealed off during movement of the drive member in one direction but ispermitted to move relative to its position inthe reverse direction ofmovement of the driving member.

The drive member may be coupled to and the variable spacing deviceconnected to the same force applying member.

The cylinder may be connected with an accumulator for liquid through avalve which is closed during movement of the drive member in the firstdirection and opened during movement in the opposite direction to permittransfer of liquid between the cylinder and accumulator.

The force applying members are usually in the form of blade holders andthere may be additional means acting on at least the blade carrierassociated with the variable spacing device to retain the associatedblade in contact with the work during the return movement of the drivemember. These means may comprise one or more piston and cylinderassemblies which are operable to return the blade holder to a startingposition relative to the drive member after shearing has been effected.

In order that the invention may be more readily understood it will nowbe described, by way of example only, with reference to the accompanyingdrawings in which:

FIG. 1 shows schematically a shear according to one embodiment of theinvention with its hydraulic circuit,

FIG. 2 shows schematically a shear in accordance with a secondembodiment of the invention, and

FIG. 3 shows schematically a shear in accordance with a still furtherembodiment of the invention.

Referring to FIG. 1, a shear is constituted by an upper blade 12 and alower shear blade 13, carried respectively by blade holders, 14, 15. Theupper blade holder 14 is driven by a reciprocating driving member, shownas a crosshead 16 mounted on a rotary eccentric 17 and acting on theblade holder 14 through a variable spacing device, which takes the formof a piston 18 sliding in a cylinder 20 formed in the blade holder14-interposed between the crosshead 16 and the piston 18 is a ladderbearing schematically indicated at 21; alternatively the crosshead 16may be replaced by a pitman mounted on the eccentric l7 and pivotallyconnected to the piston.

Return piston 22 and cylinder 23 assemblies are connected between thecrosshead 16 and brackets 24 on the blade holder 14. The crosshead isadditionally biased upwardly by the piston and cylinder assemblies 25.

The hydraulic circuit is also illustrated in the figure. The cylinder 20is connected through a pipe 26 passing through piston 18 and prefillvalve 27 to an accumulator 28, which contains liquid, such as water, andwhich is subjected to moderate gas pressure, e.g., psi.

A motor 30 drives a pump 31 which takes liquid from a tank 32 and passesit via non-return valve 33 and line 34 to accumulators 35, the pressurebeing maintained at a relative high value, such as 2700 psi.

Line 34 is connected to the assemblies 25 and to valves 36, 37 and 38,all of which are shown in their deenergized state. Valve 36, whenactuated by its solenoid 40 applies pressure to open prefill valve 27.Vale 37, when its solenoid 41 is de-energized, connects line 34 via line39 to cylinders 23 above the pistons 22; when solenoid 41 is energizedthis connection is broken. When solenoid 42 of valve 38 is energized,line 34 is connected to cylinders 23 below pistons 22 through throttlevalve 43, non-return valve 44 and line 45; when its solenoid 48 isenergized, throttle valve 43 is connected to drain and line 34 isconnected so as to open valve 44. A further valve 46 when operated byits solenoid 47 connects line 39 with throttle valve 43.

The throw of eccentric 17 is small compared with the maximum thicknessof workpiece to be cut; for example the throw may be 1% inch against amaximum workpiece thickness of 14 inches. Cutting is effected in anumber of revolutions of the eccentric, each performing a cut of ratherless than twice the throw, and the blade 12 remaining in contact withthe workpiece after each downward movement of the crosshead, so that thenext eccentric revolution performs the next cut.

With the workpiece on the blade 13, the blade holder 14 is made toapproach the workpiece by energizing solenoid 40, putting cylinder 20into communication with accumulator 28, and energizing solenoids 41, 42and 47. Pressure is applied to both ends of each of cylinders 23 and asthe lower surface of each cylinder has a greater effective area than theupper, the blade holder 14 is caused to move down until brought to restby the workpiece.

The eccentric is now rotated causing the crosshead 16 and piston 18 toreciprocate vertically. The energization of solenoid 40 is synchronizedwith the movement of the crosshead, being de-energized during the downstroke and energized during the up stroke; solenoids 41, 42, 47 remainenergized.

During each down stroke of crosshead 16, the deenergization of solenoid40 closes valve 27 and causes the liquid in cylinder 20 to be sealedoff. The downward movement of piston 18 is therefore transmitted toblade holder 14 with only a small reduction due to the compressibilityof the trapped liquid, and the work is cut. During the return upwardmovement of the crosshead, valve 27 is open and, although the piston 18follow the crosshead upwards by virtue of the pressure ofliquid in thecylinder 20, the blade holder 14 remains stationary with the blade 12 incontact with the work because of the downward force applied by liquid incylinders 23. On the next downward stroke of the crosshead, valve 27 isagain closed so that the blade holder 14 is again driven down, and afurther out is effected. The cutting cycles are continued until the workhas been sheared.

After shearing, the blade holder is returned to its original positionrelative to the cylinder 18 and crosshead 16. This is effected byenergizing solenoid 40, to open valve 27, and solenoid 48 to connectthrottle valve 43 to drain. Solenoid 47 is de-energized closing valve46, and solenoid is de-energized connecting line 39 to line 34. Pressureis thus applied above the pistons 22 driving the blade holder 14upwards, while liquid driven out of the cylinders through line 45 passesvalve 44 and is discharged to drain through valve 38 and valve 46.

The hydraulic nature of the variable spacing device (the piston 18 andcylinder 20) between the eccentric 17 and the blade holder 14 permitsthe relative movement between the blade holder and the crosshead to takeplace in the small time interval available during the upward returnmovement of piston 18, and without the use of excessively high powermotors. Thus the motor may have a power of say horse-power, which wouldneed to be drastically increased if the spacing device took the form ofmotor driven screws.

Referring now to the embodiment of the invention illustrated in FIG. 2,a rigid frame 50 supports a cylinder 51 containing a piston 52 which issecured or forms part of an upper blade holder which supports a blade53. A pair of brackets on the blade holder are connected to a pair ofcylinders 54 each containing a piston 55. The pistons are secured to theframe 50.

The lower blade 56 is positioned in a blade holder 57 which defines acylinder 58. The cylinder is connected to a pair of additional cylinders59 each containing a fixed piston 60. A piston 61 is reciprocatable inthe cylinder 58 by means of a rotary eccentric 62 and a pitman 63. Thepiston 61 and cylinder 58 constitute the variable spacing device. Thetwo cylinders 58 and 51 are connected via a pre-fill valve 27 to anaccumulator 28. The hydraulic circuit is essentially the same as thatshown in FIG. l.

The workpiece to be sheared is positioned with the shear blades engagingopposite surfaces. The two cylinders 51 and 58 are pre-filled withliquid and the valve 27 is closed. The drive member is then operated tolift the lower shear blade into shearing relation with the workpiece. Asthe piston 61 is lowered the pre-fill valve is opened to allow thecylinder 58 to be topped up while the piston-cylinder devices 59 60 keepthe lower blade holder in contact with the workpiece. The valve 27 isthen closed and the shearing operation repeated as many times as isnecessary to sever the workpiece. The piston-cylinder devices 54 55serve to raise the upper blade holder from the workpiece after theshearing operation has been completed.

In the arrangement shown in FIG. 3 the variable spacing device isassociated with one force applying member, the lower blade holder, andthe drive member is associated with the upper blade holder. I

The upper blade is carried in a holder 71 which is pivotably secured toa pitman 72. The pitman is reeiprocated by a rotary eccentric 73. Thelower blade is secured in a holder 74 which constitutes a piston in astationary cylinder 75. A pair of piston-cylinder devices 76 areattached to lugs extending from the blade holder and are anchored to arigid frame 77. The cylinder is connected through a line 77 to apre-fill valve 27 and to an accumulator 28.

In use the workpiece is brought by the lower blade holder into contactwith the upper blade. Thevalve 27 is closed and a cutting action of theupper blade is brought about. The workpiece is lifted by the lower bladeholder into engagement with the returned upper blade and a furthercutting operation is carried out.

In accordance with the provisions of the patent statutes, I haveexplained the principle and operation of my invention and haveillustrated and described what I consider to represent the bestembodiment thereof.

I claim:

l. A shear comprising an upper shear blade arranged in cooperation witha lower shear blade to sever a workpiece placed therebetween, saidblades being supported in upper and lower blade holders respectively, atleast one of the blade holders being displaceable in guides in thedirection towards the other blade holder and said displaceable bladeholder having hydraulic means associated therewith for displacing theholder and its blade until the separation of the blades is equal to thethickness of the workpiece to be severed, drive means having areciprocating action in alternate first and second opposite directions,and wherein in said first direction of reciprocation the drive means iscoupled to one of said blade holders to displace said blade holder inthe direction towards the other blade holder through a distance which issmall compared with the original separation of the blades, to produce acut in the workpiece and hydraulic means for holding said blades incontact with the workpiece during the movement of the drive means insaid second direction.

2. A shear as claimed in claim 1 in which the drive means is a rotatableeccentric member associated with a crosshead.

3. A shear as claimed inclaim 1- in which the drive means is a rotatableeccentric member associated with a pitman.

4. A shear as claimed in claim 1 in which the hydraulic means forholding the blades in contact comprise a piston displaceable in acylinder defined in the blade holder associated with the drive means,said piston being permanently connected to the drive means, and valvemeans associated with the cylinder, said valve means serving to lock asupply of liquid under pressure in the cylinder during the movement ofthe drive means in the first direction and to connect said cylinder witha source of liquid under pressure during the movement of the drive meansin said second direction.

5. A shear as claimed in claim 4 in which the lower blade and its holderare fixed and the drive means is associated with the upper blade holder.

6. A shear as claimed in claim 5 in which the hydraulic means fordisplacing the upper blade holder to initially set the separation of theblades comprise pistoncylinder devices connected between the drive meansand the upper blade holder and said devices additionally serve to keepthe upper blade in contact with the workpiece during movement of thedrive means in the second direction.

7. A shear as claimed in claim 4 in which the drive means is associatedwith the bottom blade and the upper blade is displaceable towards andaway from the lower blade by the hydraulic means for initially settingthe gap between the blades.

8. A shear as claimed in claim 7 in which the upper force-applyingmember is displaceable vertically by a piston-cylinder device and thecylinder of the device is connected with an accumulator for liquidthrough a valve which is closed during the shearing operation.

9. A shear as claimed in claim 1 in which the drive means is associatedwith the upper blade holder and the hydraulic means for holding theblades in contact with the workpiece is associated with the lower bladeholder and arranged to lift the workpiece in contact with the upperblade during movement of the drive means in the second direction.

1. A shear comprising an upper shear blade arranged in cooperation witha lower shear blade to sever a workpiece placed therebetween, saidblades being supported in upper and lower blade holders respectively, atleast one of the blade holders being displaceable in guides in thedirection towards the other blade holder and said displaceable bladeholder having hydraulic means associated therewith for displacing theholder and its blade until the separation of the blades is equal to thethickness of the workpiece to be severed, drive means having areciprocating action in alternate first and second opposite directions,and wherein in said first direction of reciprocation the drive means iscoupled to one of said blade holders to displace said blade holder inthe direction towards the other blade holder through a distance which issmall compared with the original separation of the blades, to produce acut in the workpiece and hydraulic means for holding said blades incontact with the workpiece during the movement of the drive means insaid second direction.
 2. A shear as claimed in claim 1 in which thedrive means is a rotatable eccentric member associated with a crosshead.3. A shear as claimed in claim 1 in which the drive means is a rotatableeccentric member associated with a pitman.
 4. A shear as claimed inclaim 1 in which the hydraulic means for holding the blades in contactcomprise a piston displaceable in a cylinder defined in the blade holderassociated with the drive means, said piston being permanently connectedto the drive means, and valve means associated with the cylinder, saidvalve means serving to lock a supply of liquid under pressure in thecylinder during the movement of the drive means in the first directionand to connect said cylinder with a source of liquid under pressureduring the movement of the drive means in said second direction.
 5. Ashear as claimed in claim 4 in which the lower blade and its holder arefixed and the drive means is associated with the upper blade holder. 6.A shear as claimed in claim 5 in which the hydraulic means fordisplacing the upper blade holder to initially set the separation of theblades comprise piston-cylinder devices connected between the drivemeans and the upper blade holder and said devices additionally serve tokeep the upper blade in contact with the workpiece during movement ofthe drive means in the second direction.
 7. A shear as claimed in claim4 in which the drive means is associated with the bottom blade and theupper blade is displaceable towards and away from the lower blade by thehydraulic means for initially setting the gap between the blades.
 8. Ashear as claimed in claim 7 in whIch the upper force-applying member isdisplaceable vertically by a piston-cylinder device and the cylinder ofthe device is connected with an accumulator for liquid through a valvewhich is closed during the shearing operation.
 9. A shear as claimed inclaim 1 in which the drive means is associated with the upper bladeholder and the hydraulic means for holding the blades in contact withthe workpiece is associated with the lower blade holder and arranged tolift the workpiece in contact with the upper blade during movement ofthe drive means in the second direction.